It is known in the prior art to provide bin level indicators or control devices for use in bins or the like to indicate, as by operating an electrical control switch, when granular material or the like rises in the bin to the level being monitored by the bin level indicator. The switch can be employed to actuate an alarm, to stop the flow of the granular material into the bin, or to cause the discharge of the granular material from the bin.
One common type of bin level indicator or control device is the rotary paddle type, in which the control device comprises a rotary paddle wheel or drag member which is normally rotated freely by an electric motor. When the granular material rises sufficiently in the bin to come into contact with the rotary paddle wheel, the granular material impedes or stops the rotation of the paddle wheel, whereupon the control switch in the bin level indicator is operated. Many bin level control devices of this type are of the general construction represented by the Fleckenstein U.S. Pat. No. 4,095,064 and the Sweet U.S. Pat. No. 4,211,966. In this general construction, the entire electric drive motor is mounted on a swingable or swivel support and is adapted to swing or swivel against the biasing action of a spring, when the torque reaction on the motor increases due to the increasing drag or stoppage of the rotary paddle wheel, when the granular material comes into contact with the paddle wheel. The swinging or swiveling movement of the electric motor operates the electrical control switch. This construction has the disadvantage that the electric drive motor has a significant mass and weight, which may tend to result in false signals, when the level control device is subjected to high levels of vibration.